Calculating Cycle And Reaction Times - Siemens SIMATIC S7-400H System Manual

16.6

Calculating cycle and reaction times

Cycle time
1. Using the Instruction List, determine the runtime of the user program.
2. Calculate and add the transfer time for the process image. You will find guide values for
3. Add to it the processing time at the cycle checkpoint. You will find guide values for this in
4. Multiply the calculated value by the factor in Table 15–7.
The result is the cycle time.
Extension of the cycle time due to communication and interrupts
5. Multiply the result by the following factor:
6. Using the instruction list, calculate the runtime of the program elements processing the
The result you obtain is approximately the actual cycle time. Make a note of the result.
Table 16-12 Example of calculating the reaction time
Shortest reaction time
7. Next, calculate the delays in the inputs and
outputs and, if applicable, the cycle times on the
PROFIBUS DP network.
8. The result you obtain is the shortest reaction
time.
S7-400H
System Manual, 09/2007, A5E00267695-03
this in the tables starting at 15-3.
Table 15–8.
100
100 – "configured communication load in %"
interrupts. To do so, add the relevant value from Table 15-9.
Multiply this value by the factor from step 4.
Add this value to the theoretical cycle time as often as the interrupt is triggered or is
expected to be triggered during the cycle time.
S7-400 cycle and reaction times
16.6 Calculating cycle and reaction times
Longest reaction time
7. Multiply the actual cycle time by the factor 2.
8. Next, calculate the delays in the inputs and
outputs and the cycle times on the PROFIBUS DP
network.
9. The result you obtain is the longest reaction
time.
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